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          <th width="60%" align="center">Chapter 10.  The Berkeley DB Environment </th>
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            <p>
                <span class="bold"><strong>I'm using multiple processes to
                access an Berkeley DB database environment; is
                there any way to ensure that two processes don't
                run transactional recovery at the same time, or
                that all processes have exited the database
                environment so that recovery can be
                run?</strong></span>
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            <p>
                See <a class="xref" href="transapp_fail.html" title="Handling failure in Transactional Data Store applications">Handling failure in Transactional Data Store applications</a> and <a class="xref" href="transapp_app.html" title="Architecting Transactional Data Store applications">Architecting Transactional Data
        Store applications</a> for a full
                discussion of this topic. 
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            <p>
                <span class="bold"><strong>How can I associate application
                information with a <a href="../api_reference/C/db.html" class="olink">DB</a> or <a href="../api_reference/C/env.html" class="olink">DB_ENV</a>
                handle?</strong></span>
            </p>
            <p>
                In the C API, the <a href="../api_reference/C/db.html" class="olink">DB</a> and <a href="../api_reference/C/env.html" class="olink">DB_ENV</a> structures each
                contain an "app_private" field intended to be used to
                reference application-specific information. See the
                <a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a> and <a href="../api_reference/C/envcreate.html" class="olink">db_env_create()</a> documentation for more
                information. 
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            <p>
                In the C++ or Java APIs, the easiest way to
                associate application-specific data with a handle is
                to subclass the <a href="../api_reference/CXX/db.html" class="olink">Db</a> or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a>, for
                example subclassing <a href="../api_reference/CXX/db.html" class="olink">Db</a> to get MyDb.
                Objects of type MyDb will still have the Berkeley DB
                API methods available on them, and you can put any
                extra data or methods you want into the MyDb class. If
                you are using "callback" APIs that take <a href="../api_reference/CXX/db.html" class="olink">Db</a>
                or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a> arguments (for example, <a href="../api_reference/CXX/dbset_bt_compare.html" class="olink">Db::set_bt_compare()</a>)
                these will always be called with the <a href="../api_reference/CXX/db.html" class="olink">Db</a> or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a>
                objects you create. So if you always use MyDb objects,
                you will be able to take the first argument to the
                callback function and cast it to a MyDb (in C++, cast
                it to (MyDb*)). That will allow you to access your
                data members or methods.
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